This project aims to: 1. define the immunologic stimuli which lead to tissue eosinophilia, and to determine the function of eosinophils at extravascular sites, 2. determine the metabolism of eosinophils while at rest and while engaged in the act of phagocytosis, 3. assess the presence of histamine in eosinophils, 4. study the effects of anti-eosinophil antibody on eosinophil functions in vitro and in vivo, 5. breed a strain of guinea pigs for an eosinophil-prone trait.